statue = false;
function print_nine(){
    if(statue){
        return;
    }
    var tb = document.getElementById("99");
    for(i=0;i<10;i++){
        var tr = tb.insertRow();
        for(j=0;j<i;j++){
            var td = tr.insertCell();
            console.log(td);
            td.innerHTML = (j+1) + " * " + (i) + " = " + ((i)*(j+1));
        }
    }
    statue = true;
}
function delet(){
    var tb = document.getElementById("99");
    j=10
    for(i=0;i<j;i++){
         tb.deleteRow(i);
         j--;
         i--;
    }
    statue = false;
    alert("重置成功");
}